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t trigger optimization in CMS Tracker

Workshop on B/tau Physics at LHC Helsinki, May 30 - June 1, 2002. t trigger optimization in CMS Tracker. Giuseppe Bagliesi On behalf of t tracking group. Outline. HLT Pxl and Tk results with 3+2 and 2+1 pixel layout. CPU performances for Pxl and Tk Charged Higgs with Tracker

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t trigger optimization in CMS Tracker

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  1. Workshop on B/tau Physics at LHC Helsinki, May 30 - June 1, 2002 t trigger optimization in CMS Tracker Giuseppe Bagliesi On behalf of t tracking group

  2. Outline • HLT • Pxl and Tk results with 3+2 and 2+1 pixel layout. • CPU performances for Pxl and Tk • Charged Higgs with Tracker • Off Line • Tau tagging: • Preliminary studies on mass reconstruction G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  3. High Level Trigger • Low luminosity: 2x1033 cm-2 sec-1 • ORCA 4_5_4, CMSIM 120 • Reading the DB with ORCA_5_3_4 • gg  (bb) A/H(200,500)  (bb) tt 2 t-jets+X • Final Goal is to achive a rejection factor ~ 1000 after L1 • gb  t H  t n  t- jet + 3Jets • Final Goal is to achieve a rejection factor  30 after L1 and Missing ET cut. PRELIMINARY RESULTS! • High Luminosity: 1034 cm-2 sec-1 • ORCA 6_1_0 G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  4. A. Nikitenko G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  5. leading track signal cone jet matching cone DR = 0.1 jet axis isolation cone reg Tk cone signal vertex Isolation Algorithms Signal vertex identified by: Pxl: leading track (PT>3GeV) Trk: best signal vertex candidate from pixel reconstruction. Both algorithms count number of tracks inside signal (NSIG) cone and isolation cone (NISO). Events is accepted if leading track exists andNSIG = NISO Pxl:use pixel lines (i.e. tracks reconstructed only with pixel layers). Trk: use regional tracker reconstruction. G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  6. A. Nikitenko G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  7. A. Nikitenko G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  8. A. Nikitenko ORCA 6_1_0: Pixel isolation (I)H(500GeV) -> 2t->jets Preliminary first jet is OK, small drop in efficiency due to more pxl. ineff. put in orca6. Second jet is OK for low lumi. Why it’s so bad for high lumi ? it’s due to way of finding 2-nd jet at Lvl- 2. Sasha is tuning the L2 cuts for high Lumi G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  9. A. Nikitenko ORCA_6_1_0: pixel isolation (II)QCD background (PT: 50-80 GeV) Preliminary degradation of the rejection for qcd background due to the same reasons as for the signal G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  10. A. Nikitenko Preliminary G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  11. A. Nikitenko Preliminary G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  12. A. Nikitenko Preliminary G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  13. H -> ttHLT with full track reconstruction • A “must”: decrease CPU time… • First approach: • Reconstruct tracks only around a region of interest: regional tracking with a DetUnit filter • Second approach: • seed selection in the region of interest • Conditional Track Finder: stop trajectory builder @ 6 hits • Selection much faster than with regional tracking, but loose~5%signal efficiency and decrease bkg rejection of~ 10 % • Next approach (in progress…) • NewSeedGenerator “regional” • Optimization of the ROI… • Fast (optimized) track finder (ORCA_6_1_1) G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  14. A similar approach should be used for the regional seeding CMS IN-2001/045 G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  15. H(500GeV) -> 2t->jets with tracker (ORCA_6_1_0)Comparison with Calo+Pxl (Low Lumi) Preliminary Similar Performances G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  16. H(500GeV) -> 2t->jets with tracker (ORCA_6_1_0)Comparison with Calo+Pxl (High Lumi) Preliminary Similar Performances G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  17. 3+2 2+1 H  2t  2 Jets Selection with Tracker:performances (low luminosity) (ORCA_5)Full/Staged Pixel scenario comparison G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  18. RISO=0.45 RSIG=0.065 LT Jet RM=0.1 RREG = 0.45 How to reduce tracking timein the isolation algorithm • Reconstruct tracks inside RM only • Find LT: • If LT doesn’t exists stop everything • If LT exists apply isolation on rec Tk, if it is not isolated stop everything • If event is isolated go on reconstructing also tracks inside region between RM and RREG • Apply isolation to all tracks. • Depending on bkg sample and pixel staged scenario a CPU time reduction varying from 20% to 40% is obtained G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  19. Track reconstruction timeLow luminosity (ORCA_5) Tracker Reconstruction steps (for single jet) :Time (sec) 3+2/2+1 (1 GHz cpu) G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  20. H+t nj nn Selection with Tracker (I) • Low luminosity: 2x1033 cm-2 sec-1 • 3+2 pixels scenario (preliminary 2+1) • Higgs mass = 200, 400 GeV/c2 • L1 Calo = 1 t-jet, ET > 80 GeV • L2 = Missing ET (MET) + L2 Tk: • MET > 80 GeV • L2 Tk: isolation + hard ptcut on leading track • Final Goal is a bkg rejection 30 after MET cut. • Preliminary results at 1034 cm-2 sec-1 G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  21. MET and isolation cut correlation H+->tn QCD background Missing ET cut and L2Tk selection are almost uncorrelated To increase statistics no MET cut has been applied on plots. G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  22. ORCA_5 best result S. Gennai H+/- -> tn->jet with tracker (ORCA_6_1_0) Preliminary NO MET cut, Low Lumi Ntrk=1,3 G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  23. H+t nj nn Selection with Tracker (III)3+2 Pxl and 2+1 Pxl comparison(ORCA_5) RM=0.1, RS=0.065, RI=0.4 PTLTCUT = 1. – 25. GeV RM=0.1, RS=0.065, RI=0.4 PTLTCUT = 1. – 25. GeV Staged Scenario 3+2 2+1 G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  24. S. Gennai H+/- -> tn->jet with tracker (ORCA_6_1_0) Preliminary NO MET cut, High Lumi Ntrk=1,3 Performances similar to Low Lumi G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  25. Off Line tau tagging • Preliminary studies on reconstructed tau mass in hadronic tau decays • To do: • ORCA_6_1_0 (in progress…) • Combination with vertex reconstruction • po reconstruction G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  26. S. Dutta Preliminary results on tau mass tag Preliminary • ORCA_6_1_0 • events passing LVL1 selection • Arbitrary units • (normalization on number of entries) • At least one (or three) tracks in the reconstruction cone • p0 are taken from MC truth. • R<0.4 around the jet direction • Et > 1 GeV Ntk>0 Ntk>2 G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

  27. Conclusions • H->tt->jets: • ~ 45% (30% with ORCA_6???) efficiency with ~2x103 QCD rejection is achievable at L2 (both with Calo + Pxl and Trk + Pxl) • 3+2 Vs 2+1 scenario: • Pxl can get the same efficiency and bkg rejection using also L2Calo • Trk has decrease in efficiency of ~ 10% (@ the same Bkg Rate) • Charged Higgs (L2TK isolation) • Signal Eff. ~ 50% with Bkg Rej ~ 30 • Timing (low luminosity): • Pxl can identify taus in less 50 msec • Tk can identify single tau in ~192 msec (Single t with hard PT cut) • Work in progress … • High luminosity • Timing • Performances • Off Line Tagging (mass + vertex tag) G. Bagliesi – bTau workshop – Helsinki 30/5–1/6

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